1. Field of the Invention
The invention relates to an image reading apparatus and an image forming apparatus provided with the same.
2. Related Background Art
For example, a copying machine which is an example of an image forming apparatus is provided with an image reading apparatus for reading the image of an original. The image reading apparatus is provided with image reading means for reading the image of an original, and an automatic original feeding apparatus for conveying the original to be read to a predetermined reading position.
When in such an image reading apparatus, the image of an original is to be read, the original is placed on the original placing portion of the automatic original feeding apparatus, and thereafter the original is conveyed onto an original plate. After the original has been conveyed onto the original plate, the image of the original is read by the image reading means (see Japanese Patent Application Laid-Open No. 2002-049188 and Japanese Patent Application Laid-Open No. 2003-046728.)
FIG. 6 of the accompanying drawings shows an example of such a conventional image reading apparatus. In FIG. 6, the letter A designates an image reading portion, and the letter B denotes an automatic original feeding apparatus. The automatic original feeding apparatus B is mounted so as to cover the upper surface of an original plate 101 provided on the image reading portion A.
The automatic original feeding apparatus B has an original placing portion U101 in which an original placing portion 102 is provided, and an original feeding portion U102 for separating and feeding originals from a bundle of originals G placed on the original placing portion 102 one by one. The automatic original feeding apparatus B further has an original conveying portion U103 provided with a conveying belt 104 passed over a drive roller 105 and a driven roller 106 and also, pressed against the original plate 101 by belt pressing runners 107a-107d. The automatic original feeding apparatus B is provided with an original reversing and discharging portion U104 for reversing and discharging the original G after read.
Also, the image reading portion A has a fluorescent lamp 115 as illuminating means for illuminating the original on the original plate 101. The image reading portion A has a reflector 116 for conveying illuminating light emitted from the fluorescent lamp 115 onto the surface of the original. The image reading portion A has a first mirror 117 for turning back the reflected light from the original. A first scanning optical portion 113 provided in the image reading portion A has the fluorescent lamp 115, the reflector 116 and the first mirror 117. The image reading portion A has a second scanning optical portion 114 provided with a second mirror 118 and a third mirror 119 for turning back the light from the first mirror 117. The image reading portion A is provided with a lens 120 through which the light from the second scanning optical portion 114 passes, and a CCD sensor (image reading element) 121 on which the light having passed through the lens 120 is incident and which photoelectrically converts the image information of the original.
Here, the first scanning optical portion 113 and the second scanning optical portion 114 constituting an image reading unit are guided by a rail member (not shown) and are held for movement in the image reading portion A in the direction indicated by the arrow D or the direction indicated by the arrow J. Design is made such that when the original G is placed with the original reference C of an image reading position on the original plate 101 as the reference, the first and second scanning optical portions 113 and 114 are moved and scan in the direction indicated by the arrow D to thereby read the image of the original. The second scanning optical portion 114 is moved in synchronism with the first scanning optical portion 113 so that during scanning the optical path length may be constant.
Description will now be made of the original image reading operation of the image reading apparatus constructed as described above.
When the image of an original is to be read, the uppermost one of the originals G placed on the original placing portion 102 is separated and conveyed by the original feeding portion U102. Then, the thus separated and conveyed uppermost original G is directed to a pair of registration rollers 103a and 103b. The original directed to the pair of registration rollers 103a and 103b has its skew feed corrected by the pair of registration rollers 103a and 103b, and thereafter is conveyed to the original conveying portion U103. After conveyed to the original conveying portion U103, the original goes into between the conveying belt 104 pressed against the original plate 101 and the original plate 101.
When the original G goes onto the original plate 101, the conveying belt 104 is rotated. By the conveying belt 104 being rotated, the original G is conveyed in the direction indicated by the arrow D on the original plate 101 by the frictional force of the conveying belt 104. Thereafter, when the upstream side edge (hereinafter referred to as the trailing edge) H of the original G conveyed by the conveying belt 104 with respect to the conveying direction of the original arrives at the original reference C of the image reading position on the original plate 101, the conveying belt 104 is stopped, and the original G is stopped. This original reference C of the image reading position is generally located on the left side (original feeding portion side) of the original plate 101.
Next, when the original G is thus stopped, the first and second scanning optical portions 113 and 114 are moved and scan in the direction indicated by the arrow D, and during this movement and scanning, the light from the fluorescent lamp 115 is applied to the original. Thereafter, the reflected light from the original is conveyed by the lens 120 via the first to third mirrors 117, 118 and 119, and is imaged on the CCD sensor 121. Thereby, the image of the original is read.
Next, after the termination of such original image reading, the conveying belt 104 is again rotated, whereby the original G is conveyed in the direction indicated by the arrow D, and is introduced into the original reversing and discharging portion U104 via a right jump bed 108 fixed to the right end of the original plate 101.
Here, when a one-side reading mode is set as a reading mode, the original G is reversed by the original reversing and discharging portion U104, and is again conveyed onto the original plate 101. At this time, the original G assumes a state in which the front side thereof faces upwardly.
Thereafter, the original G is discharged onto an original discharging stand 110 by the original reversing and discharging portion U104.
The discharged original G has its front side facing downwardly. By the original G being discharged with its front side facing downwardly, when the originals G are continuously discharged, the discharged originals G are stacked in the order of pages.
On the other hand, when a two-side reading mode is set as the reading mode, the original G is conveyed to the original plate 101 with its unread back side facing downwardly, by the original reversing and discharging portion U104.
Next, the original G is conveyed in the direction indicated by the arrow J by the conveying belt 104. Via a left jump bed 111 fixed to the left end of the original plate 101, as shown in FIG. 9, the original G is conveyed to an ante-register sensor 112 provided in the original feeding portion U102 by the pair of registration rollers 103a and 103b. Thereafter, when the downstream side end (hereinafter referred to as the leading edge) N of the original G opposite to the trailing edge H with respect to the conveying direction passes between a light emitting portion 112a and a light receiving portion 112b constituting the ante-register sensor 112, the conveying belt 104 and the pair of registration 10, rollers 103a and 103b are reversely rotated to thereby convey the original G in the direction indicated by the arrow D.
When the original G is thus conveyed in the direction indicated by the arrow D, the leading edge N thereof is again detected by the ante-register sensor 112. If design is made such that as described above, the original G is conveyed by a predetermined amount from a point of time at which the leading edge N has been detected, the original G can be stopped at the original reference C of the image reading position. Even if the size of the original G is changed, the amount of conveyance from the point of time at which the ante-register sensor 112 has detected the leading edge N to the original reference C of the image reading position is constant. Accordingly, it never happens that depending on the size of the original, the original stop position becomes uneven. This is also the same control in the case of the front side of the original already described.
Next, as in the case of the front side, the first and second scanning optical portions 113 and 114 are moved and scan in the direction indicated by the arrow D, whereby the image on the back side is read. Thereafter, the original G of which the images have been read is again introduced into the original reversing and discharging portion U104.
Then, the original G is discharged to the original discharging stand 110 by the original reversing and discharging portion U104. At this time, the discharged original G has its front side facing downwardly, and as in the case of the one-side reading mode, the originals G continuously discharged are stacked in the order of pages.
Now, in the case of the one-side reading mode, the front and second scanning optical portions 113 and 114 are moved in the direction indicated by the arrow J and returned to a standby position shown in FIG. 6 after the reading of the image of the original, and thereafter stand by until the next original is placed with the original reference C of the image reading position as the reference.
Also, in the case of the two-side reading mode, the first and second scanning optical portions 113 and 114 read the image on the front side of the original, and thereafter are first moved in the direction indicated by the arrow J and returned to the standby position shown in FIG. 6. Next, the original is reversed by the original reversing and discharging portion U104, and in order to read the image on the back side of the original G placed at the original reference C of the image reading position with its back side facing downwardly, the first and second scanning optical portions 113 and 114 are moved in the direction indicated by the arrow D, and thereafter are moved in the direction indicated by the arrow J and returned to the standby position.
However, in such a conventional image reading apparatus and a copying machine (image forming apparatus) provided with the same, when images on the front side and back side of an original are to be read, the image on the front side is first read at the image reading position, whereafter the original is conveyed to the original reversing and discharging portion. Next, the front side and back side of the original are reversed in the original reversing and discharging portion and the original is returned to the original plate, and thereafter is conveyed from the right end to the left end of the original plate and is returned to the original feeding portion. Thereafter, the original is again conveyed to the same image reading position as that for the front side. Therefore, the distance over which the original is conveyed is very long, thus causing a reduction in productivity.
Japanese Patent Application Laid-Open No. 2003-046728 discloses a construction in which the direction of movement of a scanner is made opposite when an original before reversal is read and when the original after reversal is read. However, in the construction of Japanese Patent Application Laid-Open No. 2003-046728, the position at which the original is stopped when the original before reversal is read and the position at which the original is stopped when the original after reversal is read are the same. Japanese Patent Application Laid-Open No. 2003-046728 bears no detailed description of the conveyance and stoppage of the original.